Dispenser-type cathode for electrical discharge tube



H. KATZ Sept. 20, 1955 DISPENSER-TYPE CATHODE FOR ELECTRICAL DISCHARGE TUBE Filed Dec. 24, 1951 aye/yaw United States Patent 2,718,607 DISPENSER-TYPE CATHODE FOR ELECTRICAL DISCHARGE TUBE Helmut Katz, Erlangen, Germany, assignor to Siemens & Halske Aktiengesellschaft, Munich, Germany, a corporation of Germany Application December 24, 1951, Serial No. 263,072 Claims priority, application Germany December 27, 1950 Claims. (Cl. 313-346) This invention is concerned with an improved dispenser-type cathode for high-vacuum electrical discharge tubes, e. g., amplifier or transmitter tubes or as electron source for electron radiation tubes.

One object of the invention is to provide a dispensertype cathode for operation in a high-vacuum tube having a porous body made, e. g., of sintered tungsten which may be oxidized if desired, such body forming an interior cavity and an exterior emission surface, a supply of emissive material in said cavity consisting of a cesium-containing substance, and means for heating said porous body and therewith said substance to cause such substance to liberate cesium for migration through the walls of said porous body to the emission surface formed thereby.

Another object is to provide a cathode body as indicated above which is made of side and end walls to form said interior cavity, said side walls forming the exterior emission surfaces.

A further object is to provide heater means for said cathode body comprising a wire surrounding such body. This wire may be directly wound upon said cathode body in insulated relation thereto and may also perform the function of a grid electrode.

Still another object is to provide an insulated heater wire surrounding the porous sintered cathode body, and another wire carried by said insulated heater wire forming a grid electrode.

The heater wire in either of the two embodiments indicated above is heated to a temperature in excess of the temperature of the emission surface to avoid precipitation of cesium vapors on the grid formed by the heater wire or carried thereby, respectively.

The heater or grid wire may be heated by alternating current of a frequency which lies outside of the operating frequency of the discharge tube in which the new cathode is used. Direct current may also be used for heating the wire, and a voltage drop may in such case be compensated by differentiated spacing of the individual Wire coils or by differentiated spacing from point to point between the porous cathode body and the grid wire so as to obtain uniform response along the entire grid formed by the wire. Both compensating features may be suitably combined. The heating wire forming the grid electrode may be a bifilar winding so as to obtain a corresponding compensation effect.

The cathode body may be heated in this manner by heat transfer from the grid wire, thus avoiding the need for separate heating means. However, if desired, separate heating means for the cathode may of course be provided.

An embodiment of the invention is shown in the accompanying drawing, in diagrammatic manner, and on an enlarged scale.

The illustrated structure comprises two porous sintered leaflike members 1 and 2 of a metal of high melting pointtungsten or the like-which are held together by the two strip-like end members 4 and 5, forming therewith an interior cavity 3. The supply 6 of emission materialcesium alone or in combination with other materials is disposed in the cavity 3. The substance is liberated and migrates through the pores of the members 1 and 2 from the inside to the outer emission surfaces thereof when these bodies reach a certain temperature. The heating means may be a heat-insulated wire 7 which is wound about the cathode body and forms a grid. The wire may be wound in bifilar fashion and on the outside thereof, facing away from the cathode bodies, may be provided a conductive layer to form the grid or an auxiliary grid electrode. The grid therefore consists, in any case, of a continuous winding. This winding may also be made of a wire bent upon itself in hairpin fashion and then wound upon the cathode body to compensate within certain limits for voltage drops in the heating current. This elfect is also obtained in a structure, made in accordance with the invention, in which the wire wound on the cathode body is only insulated therefrom upon the side which faces the porous cathode body.

It will be observed that no special heating means is required on the inside of the cathode body, the heating of such body to the required emission temperature being accomplished by the wire surrounding said body and forming a grid electrode.

Further electrodes may be provided, which have been omitted to keep the drawing simple. Opposite each of the wide sides formed by the members 1 and 2 may be disposed an anode element. These elements and the envelope of the tube have likewise been omitted to avoid encumbering the drawing.

Certain features incorporated in the disclosed cathode may be employed in cathodes of the rotary type.

Cathodes made in accordance with the invention may be used in different constructional forms for numerous purposes. They may be made in tubular form, as shown in the drawing, or in the form of diskor plate-shaped flat cathodes.

Changes may be made within the scope and spirit of the appended claims.

I claim:

1. A dispenser-type cathode for use in an electrical high-vacuum discharge tube having a sintered porous metallic cathode body comprising wall means forming an interior cavity and an exterior emitting surface, a supply of a cesium-containing emissive material disposed in said cavity, a heatable wire disposed adjacent said exterior emitting surface, said wire constituting a grid electrode.

2. The structure defined in claim 1, wherein said heatable wire is coiled about said cathode body in insulated relation thereto.

3. The structure defined in claim 1, wherein said heatable wire is disposed in bifilar fashion adjacent said exterior emitting surface.

4. The structure defined in claim 1, comprising an insulated wire coiled about said cathode body, said heatable wire being disposed upon and carried by said insulated wire and being spaced thereby from said cathode body.

5. The structure defined in claim 1, wherein said cathode body comprises a pair of relatively wide side wall means and a pair of relatively narrow end wall means, each of said side wall means forming on the outside thereof an emitting surface, said heatable wire being coiled about said cathode body in insulated relation thereto.

References Cited in the file of this patent UNITED STATES PATENTS 1,929,931 Parker Oct. 10, 1933 1,954,474 Espe et a1 Apr. 10, 1934 2,131,204 Waldschmidt Sept. 27, 1938 2,201,166 Germeshausen May 21, 1940 2,543,728 Lemmens et al Feb. 27, 1951 FOREIGN PATENTS 115,700 Great Britain May 21, 1918 

